A terminal device (e.g., a cell phone) often has multiple working modes. For example, when a “Do-Not-Disturb” mode is switched on, a cell phone of a user keeps muted or silent upon receiving a phone call or a message. In this mode, the user cannot see an unanswered call or an unread message until checking on the cell phone, while a person who makes the call hears the same voice message as in a normal calling scenario, and a person who sends the message receives the same feedback (or no feedback) as in a normal messaging scenario. In another example, when an “Airplane” mode is switched on, the cell phone is disconnected from a network. In this mode, the user cannot receive any phone call or message, while a person who makes a call hears a busy signal or a feedback indicative of unable to connect to the user, and a person who sends a message receives the same feedback (or no feedback) as in a normal messaging scenario.
A user often has to manually switch between working modes of the cell phone, and the person who makes the call (or the person who sends the message) often receives incomplete information. For example, when the called user switched to the “Do-Not-Disturb” mode, the dialer is often unaware of the situation and repeatedly calling the user. When in an emergency, the called user often cannot be reached by others if the “Do-Not-Disturb” mode or the “airplane” mode is in use.